The present invention relates to (a) novel, fluorine-containing compounds containing a special structure, that is, a fluorinated acid hydroxyl group, which may be protected, (b) fluorine-containing polymerizable monomers containing the special structure, (c) fluorine-containing polymers prepared by polymerization or copolymerization of such compounds or monomers, (d) dissolution inhibitors using those, and (e) resist compositions using such fluorine-containing compounds, monomers, fluorine-containing polymers, and dissolution inhibitors.
Fluorine-containing compounds have been used or developed in various fields particularly in the field of advanced materials due to their good qualities (e.g., water repellency, oil repellency, low water absorption, heat resistance, weather resistance, corrosion resistance, transparency, photosensitivity, low refractive index, and low dielectric property). Recently, there have been active researches and developments of fluorine-containing compounds for resist compositions and the like due to their transparency in ultraviolet region, particularly in vacuum ultraviolet wavelength region. A common aim in polymer design of such researches and developments is to achieve good adhesion to substrate and high glass transition point (hardness), while achieving transparency in each wavelength for use by introducing as many fluorine atoms as possible. For example, in the case of using a high fluorine-content polymer that has been highly fluorinated by tetrafluoroethylene or a cyclic fluorine-containing monomer, transparency in each wavelength for use is known to increase. However, there are few reports on increasing etching resistance and adhesion of fluorine-containing monomers themselves.
Recently, in next generation F2 resist field of vacuum ultraviolet region, there were reports on a hydroxyl-containing fluorostyrene (see T. H. Fedynyshyn, A. Cabral et al., J. Photopolym. Sci. Technol., 15, 655-666 (2002)) and on a hydroxyl-containing fluoronorbornene compound (see Ralph R. Dammel, Raj Sakamuri, et al., J. Photopolym. Sci. Technol., 14, 603-612 (2001)). Thus, there was emerged an idea of containing fluorine and making polarity of hydroxyl group coexistent in the molecule. However, most compounds based on such idea have disadvantages such as too high acid strength, too low glass transition point (Tg) and too low etching resistance, for example, due to their hexafluoroisopropanol (hexafluorocarbinol) structure or a secondary acid alcohol directly bonded to a cyclic fluororesin.
Although highly transparent fluororesins containing a secondary acid alcohol directly bonded to cyclic fluororesins have recently been developed, such fluororesins also have disadvantages such as too low etching resistance and too low dissolution rate upon development. Although there have been efforts for dissolving such disadvantages by nicely designing the resin skeleton, there has been a demand for the development of a fluorine-containing acid hydroxyl group containing a different structure. In other words, conventional resin skeletons are not necessarily enough in function, since they have many defects such as insufficient compatibility between transparency in ultraviolet region and etching resistance. Thus, there has been a demand for creating a novel monomer or raw material capable of providing further improved polymers, which are free of the above-mentioned defects.